/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.druid.query.operator.window.value;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import org.apache.druid.java.util.common.ISE;
import org.apache.druid.query.rowsandcols.RowsAndColumns;
import org.apache.druid.query.rowsandcols.column.ColumnAccessor;
import org.apache.druid.query.rowsandcols.column.ConstantObjectColumn;

public class WindowLastProcessor extends WindowValueProcessorBase
{
  @JsonCreator
  public WindowLastProcessor(
      @JsonProperty("inputColumn") String inputColumn,
      @JsonProperty("outputColumn") String outputColumn
  )
  {
    super(inputColumn, outputColumn);
  }

  @Override
  public RowsAndColumns process(RowsAndColumns input)
  {
    final int lastIndex = input.numRows() - 1;
    if (lastIndex < 0) {
      throw new ISE("Called with an input partition of size 0.  The call site needs to not do that.");
    }

    return processInternal(input, column -> {
      final ColumnAccessor accessor = column.toAccessor();
      return new ConstantObjectColumn(accessor.getObject(lastIndex), accessor.numRows(), accessor.getType());
    });
  }
}
